The vague message has already set off a flurry of guesses on Twitter, from the ridiculous (a Tesla salad spinner), random (Tesla farm equipment) to the wistful (a Tesla hoverboard). Some popular theories: Tesla jetpacks, batteries and bicycles. Whew.

When it comes to cryptic tweets, this isn't Musk's first rodeo. Back in October, he sparked an online frenzy when he tweeted nine enigmatic words: “About time to unveil the D and something else.” Rumors swirled wildly until Oct. 9, 2014, when Musk finally clarified what all that D talk was about, unveiling the latest upgrade to the Tesla Model S sedan. ("D stands for dual motor," he explained. "Dual motor all-wheel drive, so you have, for the first time, a model S where all wheels are providing traction.")

We probably won't know anything for sure until April 30. But until then, all guesses are welcome!

Tell Us: What will Tesla unveil at its Hawthorne Design Studio?

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